transition to multi-user.target in service files

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I8683ff7960017648e775f0c62acfd0b81a90e75d
diff --git a/service_files/phosphor-button-handler.service b/service_files/phosphor-button-handler.service
index 3771f62..79b5b05 100644
--- a/service_files/phosphor-button-handler.service
+++ b/service_files/phosphor-button-handler.service
@@ -11,5 +11,5 @@
 SyslogIdentifier=button-handler
 
 [Install]
-WantedBy=obmc-standby.target
+WantedBy=multi-user.target